1. Field of the Invention
The present invention relates to a synchronizer ring for a synchronous meshing type speed change gear and, more particularly, to a synchronizer ring for a synchronous meshing type speed change gear having a wet frictional material (i.e., a frictional material to be used in the presence of a lubricating oil, for example).
2. Related Background Art
Various synchronizer rings for a synchronous meshing type speed change gear and having a wet frictional material have previously been proposed. FIG. 1 is a diagram showing a cross sectional view of one such synchronizer ring. A wet frictional material 10b is attached to an inner surface 10a of a synchronizer ring body 10 by a method such as adhesion or the like. As shown in FIG. 2, during a speed changing operation, the wet frictional material 10b is pressed onto a frictional engaging surface 20a of a desired speed change gear 20 and synchronizes the rotation of the gear 20. The use of wet frictional material 10b provides an advantage that the operating force upon speed change decreases. On the other hand, since a lubricating oil enters the surface of the frictional material 10b, also a drawback in that there is a possibility of under-synchronization. Therefore, it has also been proposed to provide the frictional material with surface grooves such as 10c and 10d, as shown in FIG. 1, for the purpose of discharging the oil. However, even in the synchronizer ring having such a structure, the heat which is generated when the frictional material 10b comes into engagement with the frictional engaging surface 20a of the gear 20 cannot be sufficiently removed by the lubricating oil. The temperature of frictional material 10b may thus become excessive during the use of the ring, causing reduced durability.